US 5,325,663 AGranted

Diagnostic system for a secondary air supplier in an engine

AssigneeToyota Jidosha Kabushiki Kaisha

InventorTokiji Itoh

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Abstract

An engine controller executes the feedback control of an amount of the fuel injected, such that an air-fuel ratio (A/F) of the exhaust gas approaches a theoretical ratio. The amount of the fuel injected is as a function of a changeable feedback correction factor (FAF). When the engine is in a predetermined condition in which the engine controller interrupts the feedback control, a secondary air supplier supplies secondary air from an intake passage to an exhaust passage, and changes the A/F ratio of the exhaust gas. Furthermore, when the engine controller executes the feedback control operation, the secondary air is temporarily supplied to the exhaust passage, for the purpose of diagnosis of the supplier. The diagnostic system detects a first feedback correction factor before the secondary air is supplied, and a second feedback correction factor after the secondary air has been supplied, and calculates a deviation value therebetween. The system determines that the secondary air supplier is malfunctioning, when the deviation value (.DELTA.FAF) is smaller than a predetermined value (.alpha.).

Claims6

Dependent claims

A diagnostic system for a secondary air supplier in an engine, the engine including a cylinder;

an intake passage;
an exhaust passage;
an injector for injecting fuel into one of the cylinder and the intake passage;
a sensor for detecting an air-fuel ratio (A/F) of the exhaust gas within the exhaust passage;
an engine controller for executing feedback control of an amount of fuel injected by the injector, in such a way that the air-fuel ratio (A/F) approaches a theoretical air-fuel ration, wherein the amount of fuel injected is a function of a changeable feedback correction factor (FAF);
and wherein the engine controller is equipped with a memory unit for changing and storing the value of the feedback correction factor (FAF),
the secondary air supplier including an air supply unit for supplying secondary air from the intake passage to the exhaust passage, so that the secondary air mixes with existing exhaust gas to change the air-fuel ratio of the exhaust gas;
a detection unit for detecting a condition of the engine;
and a control unit for controlling the air supply unit in accordance with the engine condition, whereby the secondary air is supplied to the exhaust passage by means of the air supply unit when the engine is in a predetermined condition in which the engine controller interrupts the feedback control of the amount of the fuel injected, the diagnostic system comprising:
command means for instructing the secondary air supplier to temporarily supply air to the exhaust passage when the engine controller executes the feedback control of the amount of fuel injected;
sampling means for sampling the changeable feedback correction factor (FAF) from the memory unit, said sampling means detecting a first feedback correction factor before the secondary air is supplied based on the instruction of said command means, and a second feedback correction factor after the secondary air has been supplied;
calculation means for calculating a deviation value (.DELTA.FAF) between said first and said second feedback correction factors;
and
diagnostic means for determining that the secondary air supplier is malfunctioning when said deviation value is smaller than a predetermined value (.alpha.).

11 more elements

A method for diagnosing a secondary air supplier in an engine, the engine including a cylinder;

an intake passage;
an exhaust passage;
an injector for injecting fuel into one of the cylinder and the intake passage;
a sensor for detecting an air-fuel ratio (A/F) of the exhaust gas within the exhaust passage;
an engine controller for executing feedback control of an amount of fuel injected by the injector, in such a way that the air-fuel ratio (A/F) approaches a theoretical air-fuel ratio, wherein the amount of fuel injected is a function of a changeable feedback correction factor (FAF);
and wherein the engine controller is equipped with a memory unit for changing and storing the value of the feedback correction factor (FAF),
the secondary air supplier including an air supply unit for supplying secondary air from the intake passage to the exhaust passage, so that the secondary air mixes with existing exhaust gas;
to change the air-fuel ration of the exhaust gas;
a detection unit for detecting a condition of the engine;
and a control unit for controlling the air supply unit in accordance with the engine condition, whereby the secondary air is supplied to the exhaust passage by means of the air supply unit when the engine is in a predetermined condition in which the engine controller interrupts the feedback control of the amount of fuel injected, the method comprising the steps of:
A. determining whether the engine is in a predetermined condition suitable for diagnosing the secondary air supplier;
B. instructing the secondary air supplier to temporarily supply air to the exhaust passage, when the engine is in said predetermined condition suitable for diagnosis, and when the engine controller executes the feedback control of the amount of fuel injected;
C. detecting a first feedback correction factor before the secondary air is supplied to the exhaust passage, based on said instruction;
D. detecting a second feedback correction factor after the secondary air has been supplied to the exhaust passage, based on said instruction;
E. calculating a deviation value (.DELTA.FAF) between said first and said second feedback correction factors;
and
F. determining that the secondary air supplier is malfunctioning when said deviation value is smaller than a predetermined value (.alpha.).

14 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/042,317Filed 2 Apr 1993
Priority: JP 4-10800927 Apr 1992
Granted: 5 Jul 1994
Term ends: Not estimatedThe source records don’t support an estimate.

Classification10 codes

F01N 3/222
Control of additional air supply only, e.g. using by-passes or variable air pump drives: using electric valves only
F01N 3/22
Characterised by methods of operation; Control: control of additional air supply only, e.g. using by-passes or variable air pump drives
F01N 3/227
Control of additional air supply only, e.g. using by-passes or variable air pump drives: using pneumatically operated valves, e.g. membrane valves
F01N 11/007
Monitoring or diagnostic devices for exhaust-gas treatment apparatus: the diagnostic devices measuring oxygen or air concentration downstream of…